This invention relates to a fuel vapor processing device for a vehicle which recovers the fuel vapor produced in the fuel tank while fuel is being supplied into the tank of the vehicle.
A conventional fuel vapor processing device 200 of this type is, for example, shown in FIG. 11. A fuel tank T is connected to a fuel fill pipe T1 which is sealing closed with a fuel cap FC. A fuel branch pipe T2 is connected to the upper portion of the fuel fill pipe T1. A cut-off pipe T3 with a first fuel cut-off valve 220 is connected to the fuel tank T. A first diaphragm valve 230 is provided between the cut-off pipe T3 and the aforementioned fuel branch pipe T2. The cut-off pipe T3 is connected through the first diaphragm valve 230 and a canister-side pipe T4 to a canister (not shown).
The first fuel cut-off valve 220 comprises a valve body 222 and a coil spring 224. As fuel is fed into the fuel tank T, the fuel level FL in the fuel tank T rises, so that the valve body 222 is engaged with a seat 226 formed on the pipe T3, to prevent the flow of the fuel from the fuel tank T into the cut-off pipe T3.
The first diaphragm valve 230 comprises a first diaphragm valve body 232. The pressure of the fuel vapor in the fuel tank is applied to one side of the first diaphragm valve body 232 on the side of the cut-off pipe T3, and to the other side of the first diaphragm valve body 232 on the side of the fuel branching pipe T2. The first diaphragm valve body 232 is urged by a coil spring 233 in a direction to open the valve 230.
With the fuel cap FC removed, fuel is fed into the fuel tank through the fuel fill pipe T1. In this operation, the pressure in the fuel tank T is increased, and the internal pressure of the tank T is applied through the first fuel cut-off valve 220 to the one side of the first diaphragm valve body 232. On the other hand, the atmospheric pressure is applied to the other side of the first diaphragm valve body 232. Hence, the first diaphragm valve body 232 is opened. As a result, the fuel vapor produced in the fuel tank T flows through the first fuel cut-off valve 220, the cut-off pipe T3, the first diaphragm valve 230 and the canister-side pipe T4 to the canister (not shown), where it is recovered. Thus, the air, from which the fuel vapor has been recovered, is released to the outside.
A fuel vapor control unit 240 is provided between the fuel tank T and the canister, to allow the fuel vapor to flow between the fuel tank and the canister. The fuel vapor control unit 240 comprises a fuel vapor control pipe T5, a second fuel cut-off valve 250, and a two-way valve 270.
The second fuel cut-off valve 250 is provided to prevent the flow of the fuel from the fuel tank T to the canister when the surface of fuel in the fuel tank T is inclined, for instance, by lateral vibration of the vehicle. The second fuel cut-off valve 250 comprises a casing body 252 which accommodates a float valve body 254, and a coil spring 256 adapted to urge the float valve body 254. The float valve body 254 includes a closing protrusion 254a extended from the top. As the closing protrusion 254a is engaged with a seat 252a formed on the fuel vapor control pipe T5, to close a through-hole 252b formed in the casing body 252 through which the casing body 252 is communicated with the fuel vapor control pipe T5.
As is apparent from the above description, the second fuel cut-off valve 250 thus constructed operates as follows: When the fuel tank T is inclined, and the fuel level FL is raised to move the float valve body 254 upwardly, the closing protrusion 254a is engaged with the seat 252a to close the through-hole 252b, so that the flow of fuel from the fuel tank T to the canister is prevented.
A check valve 260 is provided in the upper portion of the second fuel cut-off valve 250. The check valve 260 operates to release the internal pressure of the fuel tank T when it has become difficult for the float valve body 254 to disengage from the seat 252a.
The two-way valve 270 has a partition wall 286 which divides the inside of its casing body 272 into an upper valve chamber 284 and a lower valve chamber 283. The lower valve chamber 283 accommodates a check valve 290, and is sealingly covered with a lid 292. The upper valve chamber 284 accommodates a second diaphragm valve 300, and is also sealingly covered with a lid 302.
The second diaphragm valve 300 comprises a second diaphragm valve body 304. The internal pressure of the fuel tank T is applied through the fuel vapor control pipe T5 to one side of the second diaphragm valve body 304, while atmospheric pressure and the elastic force of a coil spring 305 are applied to the other side of the second diaphragm valve body 304. Hence, when the internal pressure of the fuel tank becomes higher than the atmospheric pressure by a predetermined value, the valve 300 is opened to release (move) the fuel vapor from the fuel tank T into the canister.
The check valve 290 has a check valve body 294. The canister-side pressure is applied to one side of the check valve body 294, and the elastic force of a coil spring 296 is applied to the other side of the check valve body 294. Hence, when the internal pressure of the fuel tank T decreases to a predetermined value or less, the difference in pressure between the fuel tank T and the canister is a predetermined value and the check valve body 294 opens against the elastic force of the coil spring 296, so that the fuel vapor is returned from the canister into the fuel tank.
As is apparent from the above description, in the fuel vapor processing device 200, the second diaphragm valve body 304 and the check valve 290 are suitably opened and closed, to move the fuel vapor between the fuel tank T and the canister, thereby maintaining the internal pressure of the fuel tank T in a predetermined range of pressures.
The conventional fuel vapor processing device thus constructed is still disadvantageous in the following point: That is, in the fuel vapor processing device, in order to move the fuel vapor to the canister when fuel is fed into the fuel tank, the cut-off pipe T3, the first fuel cut-off valve 220 and the first diaphragm valve 230 are provided in the piping system which is different from the piping system in which the fuel vapor control unit 240 is provided. This arrangement makes the fuel vapor processing device intricate in arrangement, increases the number of manufacturing steps, and requires a relatively large space for installation.